I also thought so at first, but it seems that only the display of the speed is overstated, the speed that is used for internal calculations is the correct one. You can try that out very easily: Drive at constant 55 mph, then reset your average speed reading. After a few seconds it will show your "real" speed which is around 50 mph.

I tried this in my Seat Leon and there I found the speedometer to always show 5 % more than the GPS Speed. However the average speed was always exactly the same as the GPS speed.

Partly true, but legally speedometers are not allowed to read low - you should not be able to be doing a speed higher than indicated. Commonly, and with my last three cars or so, speedos read about 5% high - so if you have an indicated 70mph you're probably doing about 67mph.

I would doubt the OP's figures somewhere - either the speedo is faulty or his GPS speed is inaccurate. Usually GPS will be very accurate, but you have to remember the quality of the fix is dependant on the number of satellites that are in clear view. And I wouldn't treat any App data as gospel.

jet_andy
What's to doubt about my figures?
The Android App always indicates the same as my dedicated GPS (Tom Tom)
My Dashboard speedo indicates higher than actual speed, in keeping with the law and your statement.

The amended Road Vehicles (Construction and Use) Regulations 1986 permits the use of speedometers that meet either the requirements of EC Council Directive 75/443 (as amended by Directive 97/39) or UNECE Regulation 39.[SUP][/SUP]

This means, the speedometer must never show an indicated speed less than the actual speed. However it differs slightly from them in specifying that for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph. For example, if the vehicle is actually travelling at 50 mph, the speedometer must not show more than 61.25 mph or less than 50 mph.

As you will see from my post in the UK ( and the rest of Europe) a speedo can be minus nothing and plus around 10%. GPS is always the more accurate of the two. The digital speedo readout on an A3 is the same as the normal speedo, just translated into numbers and no more accurate.

As you will see from my post in the UK ( and the rest of Europe) a speedo can be minus nothing and plus around 10%. GPS is always the more accurate of the two. The digital speedo readout on an A3 is the same as the normal speedo, just translated into numbers and no more accurate.

Click to expand...

Agree completely but consideration should always be give to quality of GPS fix, which can be compromised under heavy tree coverage or surrounded by high buildings.
Our company vans are GPS tracked and you do occasionally see speed discrepancies outside the normal limits, although for the vast majority of the time they're bang on.
One guy in particular has his speed limiter set at 70, and his GPS track on motorways always shows 67mph.

It varies a lot and even the nature of the variation differs. One of my A3s had a speed which over-read by 10% at all speeds whereas another one was 2mph fast at all speeds. It's just manufacturing tolerances.

With the RNS-E in the 8P, you could use the engineering menus to display the GPS speed for comparison but I've yet to find out if there's such a screen on the MMI in the 8V.

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